The present invention relates to an automatic transmission.
In recent years, automatic transmissions mounted in vehicles have been designed with more speeds, such as eight forward speeds, for example. The automatic transmission must also achieve a compact arrangement for many components, such as clutches, from the standpoint of vehicle mountability.
There exists an automatic transmission (see, for example, Japanese Patent Application Publication No. JP-A-2006-342845) where two clutches have an input member in common and another input member that is not. The one clutch among the two clutches is positioned on an outer diameter side and fitted inside a clutch drum of the other clutch among the two clutches, which is positioned on an inner diameter side. The two clutches are aligned and arranged in an axial direction, thereby achieving compactness in the axial direction. The two clutches respectively include friction plates formed from multiple discs, an operating oil chamber that operates the friction plates, and a cancel oil chamber that cancels out a centrifugal oil pressure of a the operating oil chamber.
Among the two cancel oil chambers, the cancel oil chamber of the other clutch positioned on the inner diameter side is formed by a piston, a return spring, and a cancel plate on a rear surface side of the operating oil chamber. The cancel plate of the other clutch is retained by a snap ring on a boss portion of the one clutch.
In addition, an operating oil chamber and a cancel oil chamber of the one clutch positioned on the outer diameter side are structured rearward of the other clutch. The cancel oil chamber of the one clutch is also structured by a piston, a return spring, and a cancel plate. The cancel plate of the one clutch is retained by a snap ring and disposed on a clutch drum of the one clutch.